Plasmas can be used to assist in a number of processes, including the joining and heat-treating of materials. However, igniting, modulating, and sustaining plasmas for these purposes can be difficult for a number of reasons.
For example, it is known that a plasma can be ignited in a cavity by directing a large amount of microwave radiation into the cavity containing a gas. If the radiation intensity is large enough, the plasma can ignite spontaneously. However, radiation sources capable of supplying such large intensities can have several disadvantages; they can be expensive, heavy, bulky, and energy-consuming. Moreover, these large radiation sources normally require large electrical power supplies, which can have similar disadvantages.
One way of igniting a plasma with a lower radiation intensity is to reduce the pressure in the cavity. However, vacuum equipment, which can be used to reduce this pressure, can limit manufacturing flexibility, especially as the plasma chambers become large and especially in the context of manufacturing lines.
A sparking device can also be used to ignite a plasma using a lower radiation intensity. Such a device, however, only sparks periodically and therefore can only ignite a plasma periodically, sometimes causing an ignition lag. Moreover, conventional sparking devices are normally powered with electrical energy, limiting their use and position in many manufacturing environments.